How this calculator works
Resistor bands encode significant digits followed by a decimal multiplier and a tolerance. A sixth band can specify the temperature coefficient. Tolerance limits are computed around the nominal value at the specified reference conditions; they do not include temperature drift, ageing or self-heating. Read from the end that keeps the tolerance band last, checking the part datasheet if spacing is ambiguous.
Formula
R = digit number × 10^multiplier ohms. Rmin = R(1-t); Rmax = R(1+t). A coefficient of 50 ppm/K is 0.005% per kelvin in magnitude.
Worked example
Yellow, violet, red, gold gives 47 × 100 = 4700 ohms with +/-5% tolerance, or 4465 to 4935 ohms. Brown, black, black, brown, brown gives 1000 ohms with +/-1%.
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Frequently asked questions
Why do five-band parts give different values?
They use three significant digits instead of two. The following band is still the multiplier.
Is grey a digit or a tolerance?
It can be either. Its meaning depends on its band position: digit 8 or a specified precision tolerance.
Does temperature coefficient give a new resistance by itself?
No. It states the sensitivity to temperature change. You also need the reference temperature, temperature difference and coefficient sign from the component specification.